The invention relates to a device for controlling an automatic transmission having an electronic control unit. In particular, the invention relates to a device for controlling an automatic transmission having an electronic control unit and having a power control element, the control unit detecting a desired-power signal corresponding to the position of the power control element and, basically as a function of this desired-power signal, causing a change of gear corresponding to the characteristic shifting curves stored in the control unit, and the control unit generating a gradient signal corresponding to the rate of change of the desired-power signal and being able to cause a backshift deviating from the characteristic shifting curves as a function of this gradient signal.
Such a device is known, for example, from European Patent document EP 1 117 951 B1. In the case of this known device, backshifts are caused as a function of a gradient signal related to the desired power completely independently of the characteristic shifting curves. Furthermore, already caused backshifts are terminated again if the gradient signal falls below a defined lower limit value. As a result, uncomfortable pendulum shifts may occur.
It is an object of the invention to simultaneously take comfort aspects into account during shifting operations of an automatic transmission when adapting the dynamics to a driver's desired-load signal.
According to the invention, this is achieved by providing a device for controlling an automatic transmission having electronic control unit and having a power control element, the control unit detecting a desired-power signal corresponding to the position of the power control element and, basically as a function of this desired-power signal, causing a change of gear corresponding to the characteristic shifting curves stored in the control unit, and the control unit generating a gradient signal corresponding to the rate of change of the desired-power signal and being able to cause a backshift deviating from the characteristic shifting curves as a function of this gradient signal. The control unit is further developed such that an immediate backshift or multiple backshift is initiated as a function of the gradient signal when, as a characteristic shifting curve for a first backshift has been reached, the gradient signal has exceeded at least a first lower limit value.
In the case of the device according to the invention for controlling an automatic transmission having an electronic control unit and having a power control element, the control unit detects a desired-power signal corresponding to the position of the power control element and, basically as a function of this desired-power signal, causes a change of gear corresponding to the characteristic shifting curves stored in the control unit. Furthermore, the control unit generates a gradient signal corresponding to the rate of change of the desired-power signal and can—when certain conditions exist—cause a backshift deviating from the characteristic shifting curves as a function of this gradient signal. By way of the control unit, an immediate backshift, and if required, multiple backshifts, are initiated as a function of the gradient signal when, as a characteristic shifting curve for a first backshift has been reached, the gradient signal has exceeded at least a first lower limit value. The desired-power signal may correspond, for example, directly to the position of a power control element (such as the accelerator pedal or the throttle valve) or indirectly in the form of a desired torque (such as a desired engine torque or a desired wheel torque) or to a desired acceleration, both, as required, while also taking into account additional parameters.
With respect to the invention, the term “characteristic shifting curve” should be interpreted such that any fixedly stored default leading to a gear change is covered in the electronic control device. This may concern, for example, a gear change control based on characteristic shifting curves (known, for example, from European Patent document EP 0 471 102 B1) or a gear change control based on tension force (known, for example, from European Patent document EP 1 248 021 A1; here, the characteristic shifting curves are called tensile force curves).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.